Try with resources

aidanfitz

Hi. I'm trying to use Processing with Encog, and I have two functions that serialize and deserialize a neural network. The sketch contains two functions that I originally wrote in plain Java 7, so it uses try-with-resources. However, when I ran them verbatim in Processing, it gave me this error: Expected LBRACE, found '('

So I expanded out the try-with-resources, like this:

BasicNetwork load() {
  ObjectInputStream in = null;
  try {
    in = new ObjectInputStream(new FileInputStream(file));
    return (BasicNetwork) in.readObject();
  }
  catch (ClassNotFoundException e) {
    System.err.println("Looks like Encog isn't imported properly :(");
    System.exit(1);
    return null;
  }
  catch (IOException e) {
    e.printStackTrace();
    return null;
  }
  finally {
    in.close();
  }
}

But then in.close() can also throw IOException, so Processing gave me this error for the finally block:

Unhandled exception type IOException

I know, ironic. I'm gonna be playing Whac-a-Mole with these pesky exceptions. What should I do about it?

Here is my original code:

File file = new File("data/neural-network.blob");

BasicNetwork load() {
  try (ObjectInputStream in = new ObjectInputStream(new FileInputStream(file))) {
    return (BasicNetwork) in.readObject();
  }
  catch (ClassNotFoundException e) {
    System.err.println("Looks like Encog isn't imported properly :(");
    System.exit(1);
    return null;
  }
  catch (IOException e) {
    e.printStackTrace();
    return null;
  }
}

GoToLoop

• The PDE (Processing's IDE) is very faulty about Java specifications.
• Actually, it's not even fully compatible w/ Java 5! @-)
• The PDE relies on a pre-processor in order to transpile ".pde" sketches as 1 Java class.
• If we really wanna use full Java in the PDE we need to create a ".java" suffixed tab.
• However, any code from those tabs needs the PApplet reference from the ".pde" canvas.

KevinWorkman

Your code compiles fine. The only problem is that the in.close() line also needs to be wrapped in a try/catch block.

One approach would be to just wrap the whole thing in a try/catch block. That's not exactly the safest, but for most cases (particularly if this is just something for yourself and not some mission-critical piece of infrastructure) it'll do the job.

If that sounds annoying, then you understand why they added the try-with-resources feature.

quark

The LBRACE is a simple syntax error that is not related to the try-catch code posted here. You need to look at your code before the indicated error position for an extra RBRACE i.e. )

aidanfitz

Aha, I changed it to

BasicNetwork load() {
  try {
    ObjectInputStream in = new ObjectInputStream(new FileInputStream(file));
    BasicNetwork yolo = (BasicNetwork) in.readObject();
    in.close();
    return yolo;
  }
  catch (ClassNotFoundException e) {
    System.err.println("Looks like Encog isn't imported properly :(");
    System.exit(1);
    return null;
  }
  catch (IOException e) {
    e.printStackTrace();
    return null;
  }
}